Like Tree0Likes

HP 500 Heads/Cam/Intake/Carb On a 454 MAG?

Reply
Old 08-12-2010, 10:02 AM
  #1
Registered
Thread Starter
 
Join Date: Feb 2008
Posts: 140
Default HP 500 Heads/Cam/Intake/Carb On a 454 MAG?

I have a 1989 Century Ultra I with the 365 hp 454 MAG carb and Bravo outdrive. The motor is stock except for stainless marine headers and risers and has 345 hours on it. The boat runs 61 mph on GPS right now with a 23P Mirage Plus prop at 5200 rpms.

I just picked up stock heads, cam, intake and carb. off an HP 500. Is this a good upgrade? How much of an increase in hp and speed should I see? Any guesses on a prop? I know there are a lot of variables I'm just looking for some estimates.

Thanks
CenturyUltra is offline  
Reply With Quote
Old 08-12-2010, 10:12 AM
  #2
Registered
Platinum Member
 
Join Date: Jun 2006
Location: Lake Conroe, TX.
My Boats: 39' Sea Ray, 38' Nortech, 18' Taylor SJ
Posts: 14,916
Default

Quote:
Originally Posted by CenturyUltra View Post
I have a 1989 Century Ultra I with the 365 hp 454 MAG carb and Bravo outdrive. The motor is stock except for stainless marine headers and risers and has 345 hours on it. The boat runs 61 mph on GPS right now with a 23P Mirage Plus prop at 5200 rpms.

I just picked up stock heads, cam, intake and carb. off an HP 500. Is this a good upgrade? How much of an increase in hp and speed should I see? Any guesses on a prop? I know there are a lot of variables I'm just looking for some estimates.

Thanks
In order to utelize that set up, you will need to turn up the RPM's. Probably have to propr it so it turns to 6000+. The cam in a 500HP is pretty big for a 454 with very light compresion. It will work, but you will have to rev it very hard.
jeff1000man is offline  
Reply With Quote
Old 08-12-2010, 12:38 PM
  #3
Charter Member # 55
Charter Member
 
Griff's Avatar
 
Join Date: Oct 2000
Location: Omaha
My Boats: .......32............. ...............Active Thunder....
Posts: 15,752
Default

The heads on both engines are the same, except for the HP500 heads have slightly larger valves. The HP500 cams made the engines prone to reversion. Make sure the valve springs on the heads are good.

You might see a 2-3mph gain.
Griff is offline  
Reply With Quote
Old 08-12-2010, 02:31 PM
  #4
Registered
Thread Starter
 
Join Date: Feb 2008
Posts: 140
Default

well i certainly dont want to worry about reversion is this even worth doing?
CenturyUltra is offline  
Reply With Quote
Old 08-12-2010, 03:34 PM
  #5
Registered
 
mwdill's Avatar
 
Join Date: Feb 2003
Location: SML VA
My Boats: 02 HUSTLER SLINGSHOT
Posts: 2,952
Default

i have a friend that did that exact thing other than the cam he used was the same as a hp525 (741), he picked up a solid 8mph
mwdill is offline  
Reply With Quote
Old 08-12-2010, 03:57 PM
  #6
Platinum Member
Platinum Member
Trade Score: (1)
 
offthefront's Avatar
 
Join Date: Feb 2004
Location: Northeast,Fla
My Boats: 353 with Prochargers
Posts: 4,804
Default

Quote:
Originally Posted by jeff1000man View Post
In order to utelize that set up, you will need to turn up the RPM's. Probably have to propr it so it turns to 6000+. The cam in a 500HP is pretty big for a 454 with very light compresion. It will work, but you will have to rev it very hard.
I would go with the 741 cam ...or even better have Bob Madara spec one ...give Bob a call he's a straight shooter ...some head work would be nice too ....

Kinda makes me nervous thinking about a stock mag bottom end W/345hrs at 6K ...


Bob Madara
1-585-654-8583.
offthefront is offline  
Reply With Quote
Old 08-12-2010, 06:11 PM
  #7
Charter Member #1055/Moderator
Charter Member
Trade Score: (1)
 
GO4BROKE's Avatar
 
Join Date: Feb 2001
Location: CNY
My Boats: Sonic 386
Posts: 4,579
Default

Stock mag lower end is forged steel crank and rods, forged pistons. If gen 6 it has roller rockers. Its pretty stout. I wouldn't hesitate to do it if the motor has been maintained.
__________________
[img][/img]
GO4BROKE is offline  
Reply With Quote
Old 08-12-2010, 11:17 PM
  #8
Registered
Thread Starter
 
Join Date: Feb 2008
Posts: 140
Default

Thanks to all. Sounds like its worth doing. Should I be worried about reversion with the stainless marine exhaust and the HP 500 cam?
CenturyUltra is offline  
Reply With Quote
Old 08-13-2010, 02:15 AM
  #9
Charter Member # 55
Charter Member
 
Griff's Avatar
 
Join Date: Oct 2000
Location: Omaha
My Boats: .......32............. ...............Active Thunder....
Posts: 15,752
Default

IMO, there are better choices for a cam than the carb HP500cam. You will be able to make the same power with a better idle and no chance of reversion.
The HP500 cam is on a 110 lobe sep and has a ot of overlap. You would be much better off with a cam on 112-114 lob sep.
I think the 741 is too big for a 454ci engine unless you spin it up to about 5800rpms. Something closer to the 731 cam would be better for a 454 and have better midrange torque.
Griff is offline  
Reply With Quote
Reply



Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 04:47 PM.


Copyright 2011 OffShoreOnly. All rights reserved.